Where can I find which packages are available as tds.zip?
AFAIK the TDS ZIP files need to be provided by the package authors and are only then available in the http://www.ctan.org/tex-archive/install/macros/latex/contrib directory. It seems that the author of that particular package didn't uploaded a TDS ZIP file.
I also agree that the TDS ZIP files are hard to find. I wondered for a while if the ones I uploaded (together with a normal ZIP file) are really used. It would be nice if the web interface of CTAN (http://www.ctan.org/pkg/<PACKAGE>) would also link to these files.
However, the TDS ZIP file of a package is linked by the TeX catalogue entry at http://www.ctan.org/tex-archive/help/Catalogue/entries/<PACKAGE>.html under Distributions and in the package page on http://ctanhg.scharrer-online.de/pkg/<PACKAGE> under On CTAN (usually the last in the list).
If you are looking for a list of all available TDS ZIP files instead:
There is a text file which lists all files under http://mirrors.ctan.org/FILES.byname. It shows that almost all TDS ZIP files are under /install/... where ... represents their normal location on CTAN, i.e. /install/macros/latex/contrib for contributed LaTeX packages. An exception are the one which are placed in the graphics folder (e.g. PGF/TikZ supporting packages like tikz-timing). The only one there is my tikz-timing package located at /install/graphics/pgf/contrib/tikz-timing.tds.zip.
The fonts, support and info related TDS ZIP files are in the appropriate subdirectories below /install.
A full list can be produces by downloading the above mentioned FILES.byname file and use e.g. grep '\.tds\.zip' FILES.byname on it. The result is shown below. If it isn't listed there, it is not on CTAN. However, it is of course possible that the author or someone else uploaded it only on its private website or other place.
install/biblio/bibtex/contrib/gost.tds.zip
install/fonts/ae.tds.zip
install/fonts/auto1.tds.zip
install/fonts/bickham.tds.zip
install/fonts/ccicons.tds.zip
install/fonts/cm/cmtiup.tds.zip
install/fonts/cmll.tds.zip
install/fonts/countriesofeurope.tds.zip
install/fonts/doublestroke.tds.zip
install/fonts/fdsymbol.tds.zip
install/fonts/figbas.tds.zip
install/fonts/frcursive.tds.zip
install/fonts/gillcm.tds.zip
install/fonts/jamtimes.tds.zip
install/fonts/kpfonts.tds.zip
install/fonts/mathgifg.tds.zip
install/fonts/mdputu.tds.zip
install/fonts/mdsymbol.tds.zip
install/fonts/newtx.tds.zip
install/fonts/pcarl.tds.zip
install/fonts/psfonts/adobe/futurans.tds.zip
install/fonts/psfonts/adobe/nbaskerv.tds.zip
install/fonts/psfonts/emigre/dogma.tds.zip
install/fonts/psfonts/fontfabrik/thsmc.tds.zip
install/fonts/semaphor.tds.zip
install/fonts/softmakerfreefont/alteschwabacher.tds.zip
install/fonts/softmakerfreefont/artistic.tds.zip
install/fonts/softmakerfreefont/baskervillenova.tds.zip
install/fonts/softmakerfreefont/bonita.tds.zip
install/fonts/softmakerfreefont/broadway.tds.zip
install/fonts/softmakerfreefont/canossa.tds.zip
install/fonts/softmakerfreefont/congress.tds.zip
install/fonts/softmakerfreefont/delanocaps.tds.zip
install/fonts/softmakerfreefont/digital.tds.zip
install/fonts/softmakerfreefont/egyptiennestd.tds.zip
install/fonts/softmakerfreefont/flagstaff.tds.zip
install/fonts/softmakerfreefont/grenoble.tds.zip
install/fonts/softmakerfreefont/helium.tds.zip
install/fonts/softmakerfreefont/heliumtwo.tds.zip
install/fonts/softmakerfreefont/henderson.tds.zip
install/fonts/softmakerfreefont/iceberg.tds.zip
install/fonts/softmakerfreefont/inverserif.tds.zip
install/fonts/softmakerfreefont/jugendstil.tds.zip
install/fonts/softmakerfreefont/marseille.tds.zip
install/fonts/softmakerfreefont/moab.tds.zip
install/fonts/softmakerfreefont/nevada.tds.zip
install/fonts/softmakerfreefont/newcastle.tds.zip
install/fonts/softmakerfreefont/oldblackletter.tds.zip
install/fonts/softmakerfreefont/quadrat.tds.zip
install/fonts/softmakerfreefont/softmakerfreefont.tds.zip
install/fonts/softmakerfreefont/stonehand.tds.zip
install/fonts/softmakerfreefont/sunset.tds.zip
install/fonts/softmakerfreefont/tampa.tds.zip
install/fonts/softmakerfreefont/vagrounded.tds.zip
install/fonts/softmakerfreefont/velo.tds.zip
install/fonts/softmakerfreefont/veracruz.tds.zip
install/fonts/stix.tds.zip
install/fonts/thai/fonts-sipa-arundina.tds.zip
install/fonts/thai/fonts-tlwg.tds.zip
install/fonts/urw/antiqua.tds.zip
install/fonts/urw/arial.tds.zip
install/fonts/verdana.tds.zip
install/graphics/pgf/contrib/tikzpagenodes.tds.zip
install/graphics/pgf/contrib/tikz-timing.tds.zip
install/info/fifinddo-info.tds.zip
install/info/latexfileinfo-pkgs.tds.zip
install/info/luatex/lualatex-doc.tds.zip
install/info/macros2e.tds.zip
install/language/spanish/babel/base.tds.zip
install/language/thai/thailatex.tds.zip
install/language/vietnamese/vntex.tds.zip
install/macros/generic/bitelist.tds.zip
install/macros/generic/dowith.tds.zip
install/macros/generic/ifxetex.tds.zip
install/macros/latex/contrib/abstract.tds.zip
install/macros/latex/contrib/achemso.tds.zip
install/macros/latex/contrib/acronym.tds.zip
install/macros/latex/contrib/acroterm.tds.zip
install/macros/latex/contrib/addlines.tds.zip
install/macros/latex/contrib/adjustbox.tds.zip
install/macros/latex/contrib/animate.tds.zip
install/macros/latex/contrib/answers.tds.zip
install/macros/latex/contrib/appendix.tds.zip
install/macros/latex/contrib/asyfig.tds.zip
install/macros/latex/contrib/attachfile.tds.zip
install/macros/latex/contrib/auto-pst-pdf.tds.zip
install/macros/latex/contrib/bez123.tds.zip
install/macros/latex/contrib/bezos.tds.zip
install/macros/latex/contrib/biblatex-contrib/authoryear-icomp-tt.tds.zip
install/macros/latex/contrib/biblatex-contrib/biblatex-chem.tds.zip
install/macros/latex/contrib/biblatex-contrib/biblatex-dw.tds.zip
install/macros/latex/contrib/biblatex-contrib/biblatex-ieee.tds.zip
install/macros/latex/contrib/biblatex-contrib/biblatex-luh-ipw.tds.zip
install/macros/latex/contrib/biblatex-contrib/biblatex-nature.tds.zip
install/macros/latex/contrib/biblatex-contrib/biblatex-science.tds.zip
install/macros/latex/contrib/biblatex-contrib/historische-zeitschrift.tds.zip
install/macros/latex/contrib/biblatex.tds.zip
install/macros/latex/contrib/bibleref-german.tds.zip
install/macros/latex/contrib/bibleref.tds.zip
install/macros/latex/contrib/bidi.tds.zip
install/macros/latex/contrib/blowup.tds.zip
install/macros/latex/contrib/booklet.tds.zip
install/macros/latex/contrib/bytefield.tds.zip
install/macros/latex/contrib/cachepic.tds.zip
install/macros/latex/contrib/caption.tds.zip
install/macros/latex/contrib/ccaption.tds.zip
install/macros/latex/contrib/changepage.tds.zip
install/macros/latex/contrib/changes.tds.zip
install/macros/latex/contrib/chappg.tds.zip
install/macros/latex/contrib/chemstyle.tds.zip
install/macros/latex/contrib/cmpj.tds.zip
install/macros/latex/contrib/collcell.tds.zip
install/macros/latex/contrib/collectbox.tds.zip
install/macros/latex/contrib/combine.tds.zip
install/macros/latex/contrib/comicsans.tds.zip
install/macros/latex/contrib/conferences/active-conf.tds.zip
install/macros/latex/contrib/conferences/icsv.tds.zip
install/macros/latex/contrib/cpssp.tds.zip
install/macros/latex/contrib/csbulletin.tds.zip
install/macros/latex/contrib/csquotes.tds.zip
install/macros/latex/contrib/csvsimple.tds.zip
install/macros/latex/contrib/csvtools.tds.zip
install/macros/latex/contrib/currfile.tds.zip
install/macros/latex/contrib/dashrule.tds.zip
install/macros/latex/contrib/datatool.tds.zip
install/macros/latex/contrib/datetime.tds.zip
install/macros/latex/contrib/dhua.tds.zip
install/macros/latex/contrib/dlfltxb.tds.zip
install/macros/latex/contrib/docmfp.tds.zip
install/macros/latex/contrib/doipubmed.tds.zip
install/macros/latex/contrib/drac.tds.zip
install/macros/latex/contrib/droit-fr.tds.zip
install/macros/latex/contrib/dvdcoll.tds.zip
install/macros/latex/contrib/easyfig.tds.zip
install/macros/latex/contrib/edfnotes.tds.zip
install/macros/latex/contrib/endfloat.tds.zip
install/macros/latex/contrib/engpron.tds.zip
install/macros/latex/contrib/engrec.tds.zip
install/macros/latex/contrib/enumitem.tds.zip
install/macros/latex/contrib/environ.tds.zip
install/macros/latex/contrib/epigraph.tds.zip
install/macros/latex/contrib/eqparbox.tds.zip
install/macros/latex/contrib/etoolbox.tds.zip
install/macros/latex/contrib/euenc.tds.zip
install/macros/latex/contrib/everyhook.tds.zip
install/macros/latex/contrib/fancytabs.tds.zip
install/macros/latex/contrib/filecontents.tds.zip
install/macros/latex/contrib/filehook.tds.zip
install/macros/latex/contrib/fileinfo.tds.zip
install/macros/latex/contrib/filemod.tds.zip
install/macros/latex/contrib/finstrut.tds.zip
install/macros/latex/contrib/flowfram.tds.zip
install/macros/latex/contrib/fmtcount.tds.zip
install/macros/latex/contrib/fontspec.tds.zip
install/macros/latex/contrib/fonttable.tds.zip
install/macros/latex/contrib/footmisc.tds.zip
install/macros/latex/contrib/footnoterange.tds.zip
install/macros/latex/contrib/frontespizio.tds.zip
install/macros/latex/contrib/gincltex.tds.zip
install/macros/latex/contrib/gitinfo.tds.zip
install/macros/latex/contrib/glossaries.tds.zip
install/macros/latex/contrib/gmdoc.tds.zip
install/macros/latex/contrib/gmeometric.tds.zip
install/macros/latex/contrib/gmiflink.tds.zip
install/macros/latex/contrib/gmutils.tds.zip
install/macros/latex/contrib/gmverb.tds.zip
install/macros/latex/contrib/gmverse.tds.zip
install/macros/latex/contrib/gridset.tds.zip
install/macros/latex/contrib/hanging.tds.zip
install/macros/latex/contrib/hardwrap.tds.zip
install/macros/latex/contrib/he-she.tds.zip
install/macros/latex/contrib/hrefhide.tds.zip
install/macros/latex/contrib/hyperref.tds.zip
install/macros/latex/contrib/hyperxmp.tds.zip
install/macros/latex/contrib/hyphenat.tds.zip
install/macros/latex/contrib/IEEEconf.tds.zip
install/macros/latex/contrib/ifetex.tds.zip
install/macros/latex/contrib/ifmtarg.tds.zip
install/macros/latex/contrib/ifnextok.tds.zip
install/macros/latex/contrib/ifoddpage.tds.zip
install/macros/latex/contrib/ifplatform.tds.zip
install/macros/latex/contrib/imakeidx.tds.zip
install/macros/latex/contrib/impnattypo.tds.zip
install/macros/latex/contrib/imtekda.tds.zip
install/macros/latex/contrib/inputtrc.tds.zip
install/macros/latex/contrib/inversepath.tds.zip
install/macros/latex/contrib/jmlr.tds.zip
install/macros/latex/contrib/kantlipsum.tds.zip
install/macros/latex/contrib/l3experimental.tds.zip
install/macros/latex/contrib/l3kernel.tds.zip
install/macros/latex/contrib/l3packages.tds.zip
install/macros/latex/contrib/lastpage.tds.zip
install/macros/latex/contrib/layouts.tds.zip
install/macros/latex/contrib/lcyw.tds.zip
install/macros/latex/contrib/leading.tds.zip
install/macros/latex/contrib/lettrine.tds.zip
install/macros/latex/contrib/lineno.tds.zip
install/macros/latex/contrib/logreq.tds.zip
install/macros/latex/contrib/longnamefilelist.tds.zip
install/macros/latex/contrib/lstaddons.tds.zip
install/macros/latex/contrib/ltxdockit.tds.zip
install/macros/latex/contrib/makecmds.tds.zip
install/macros/latex/contrib/marginnote.tds.zip
install/macros/latex/contrib/mathalfa.tds.zip
install/macros/latex/contrib/mattens.tds.zip
install/macros/latex/contrib/mdframed.tds.zip
install/macros/latex/contrib/media9.tds.zip
install/macros/latex/contrib/memoir.tds.zip
install/macros/latex/contrib/mh.tds.zip
install/macros/latex/contrib/microtype.tds.zip
install/macros/latex/contrib/minibox.tds.zip
install/macros/latex/contrib/mlist.tds.zip
install/macros/latex/contrib/moderntimeline.tds.zip
install/macros/latex/contrib/modroman.tds.zip
install/macros/latex/contrib/monofill.tds.zip
install/macros/latex/contrib/morefloats.tds.zip
install/macros/latex/contrib/morehype.tds.zip
install/macros/latex/contrib/moreverb.tds.zip
install/macros/latex/contrib/mpgraphics.tds.zip
install/macros/latex/contrib/msu-thesis.tds.zip
install/macros/latex/contrib/mwe.tds.zip
install/macros/latex/contrib/needspace.tds.zip
install/macros/latex/contrib/newfile.tds.zip
install/macros/latex/contrib/newverbs.tds.zip
install/macros/latex/contrib/nicefilelist.tds.zip
install/macros/latex/contrib/nicetext.tds.zip
install/macros/latex/contrib/nonumonpart.tds.zip
install/macros/latex/contrib/notes2bib.tds.zip
install/macros/latex/contrib/nowidow.tds.zip
install/macros/latex/contrib/oberdiek.tds.zip
install/macros/latex/contrib/pagecolor.tds.zip
install/macros/latex/contrib/pagenote.tds.zip
install/macros/latex/contrib/pageslts.tds.zip
install/macros/latex/contrib/papermas.tds.zip
install/macros/latex/contrib/paresse.tds.zip
install/macros/latex/contrib/pax.tds.zip
install/macros/latex/contrib/pdf14.tds.zip
install/macros/latex/contrib/pdfcomment.tds.zip
install/macros/latex/contrib/pdfpages.tds.zip
install/macros/latex/contrib/pgfopts.tds.zip
install/macros/latex/contrib/probsoln.tds.zip
install/macros/latex/contrib/proposal.tds.zip
install/macros/latex/contrib/psnfssx/lucidabr.tds.zip
install/macros/latex/contrib/pstool.tds.zip
install/macros/latex/contrib/pst-pdf.tds.zip
install/macros/latex/contrib/pst-vowel.tds.zip
install/macros/latex/contrib/quotmark.tds.zip
install/macros/latex/contrib/rcs-multi.tds.zip
install/macros/latex/contrib/realboxes.tds.zip
install/macros/latex/contrib/realscripts.tds.zip
install/macros/latex/contrib/regstats.tds.zip
install/macros/latex/contrib/romanbar.tds.zip
install/macros/latex/contrib/romannum.tds.zip
install/macros/latex/contrib/rotating.tds.zip
install/macros/latex/contrib/rsc.tds.zip
install/macros/latex/contrib/sapthesis.tds.zip
install/macros/latex/contrib/savetrees.tds.zip
install/macros/latex/contrib/showlabels.tds.zip
install/macros/latex/contrib/siunitx.tds.zip
install/macros/latex/contrib/splitindex.tds.zip
install/macros/latex/contrib/spverbatim.tds.zip
install/macros/latex/contrib/standalone.tds.zip
install/macros/latex/contrib/stdclsdv.tds.zip
install/macros/latex/contrib/steinmetz.tds.zip
install/macros/latex/contrib/stellenbosch.tds.zip
install/macros/latex/contrib/stex.tds.zip
install/macros/latex/contrib/storebox.tds.zip
install/macros/latex/contrib/suftesi.tds.zip
install/macros/latex/contrib/svn-multi.tds.zip
install/macros/latex/contrib/svn-prov.tds.zip
install/macros/latex/contrib/tablefootnote.tds.zip
install/macros/latex/contrib/tabvar.tds.zip
install/macros/latex/contrib/tagging.tds.zip
install/macros/latex/contrib/tcolorbox.tds.zip
install/macros/latex/contrib/tdsfrmath.tds.zip
install/macros/latex/contrib/thumbs.tds.zip
install/macros/latex/contrib/titlesec.tds.zip
install/macros/latex/contrib/titling.tds.zip
install/macros/latex/contrib/tocbibind.tds.zip
install/macros/latex/contrib/tocloft.tds.zip
install/macros/latex/contrib/tocvsec2.tds.zip
install/macros/latex/contrib/tqft.tds.zip
install/macros/latex/contrib/trimspaces.tds.zip
install/macros/latex/contrib/trivfloat.tds.zip
install/macros/latex/contrib/tufte-latex.tds.zip
install/macros/latex/contrib/undolabl.tds.zip
install/macros/latex/contrib/unicode-math.tds.zip
install/macros/latex/contrib/uri.tds.zip
install/macros/latex/contrib/usebib.tds.zip
install/macros/latex/contrib/varsfromjobname.tds.zip
install/macros/latex/contrib/verse.tds.zip
install/macros/latex/contrib/vertbars.tds.zip
install/macros/latex/contrib/vpe.tds.zip
install/macros/latex/contrib/vwcol.tds.zip
install/macros/latex/contrib/xfor.tds.zip
install/macros/latex/contrib/xltxtra.tds.zip
install/macros/latex/contrib/xpatch.tds.zip
install/macros/latex/contrib/xtab.tds.zip
install/macros/latex/contrib/yagusylo.tds.zip
install/macros/latex/contrib/ydoc.tds.zip
install/macros/latex/required/amslatex/amscls.tds.zip
install/macros/luatex/generic/lualibs.tds.zip
install/macros/luatex/generic/luamplib.tds.zip
install/macros/luatex/generic/luaotfload.tds.zip
install/macros/luatex/generic/luatexbase.tds.zip
install/macros/luatex/latex/luabibentry.tds.zip
install/macros/luatex/latex/luacode.tds.zip
install/macros/luatex/latex/luainputenc.tds.zip
install/macros/luatex/latex/lualatex-math.tds.zip
install/macros/luatex/latex/luatextra.tds.zip
install/macros/plain/plnfss.tds.zip
install/macros/xetex/latex/arabxetex.tds.zip
install/macros/xetex/latex/polyglossia.tds.zip
install/macros/xetex/latex/xepersian.tds.zip
install/macros/xetex/plain/xetexfontinfo.tds.zip
install/support/ctanupload.tds.zip
install/support/ctanWeb/install_test.tds.zip
install/support/ctanWeb/jhtest.tds.zip
install/support/pdfcrop.tds.zip
install/support/texdef.tds.zip
install/support/thumbpdf.tds.zip
install/support/typeoutfileinfo.tds.zip
language/japanese/ptex-texmf/ptex.tds.zip
macros/latex/contrib/koma-script/komascript.tds.zip
macros/latex/contrib/latex-tds/amslatex.tds.zip
macros/latex/contrib/latex-tds/babel.tds.zip
macros/latex/contrib/latex-tds/base.tds.zip
macros/latex/contrib/latex-tds/cyrillic.tds.zip
macros/latex/contrib/latex-tds/etex.tds.zip
macros/latex/contrib/latex-tds/graphics.tds.zip
macros/latex/contrib/latex-tds/knuth.tds.zip
macros/latex/contrib/latex-tds/latex-tds.tds.zip
macros/latex/contrib/latex-tds/psnfss.tds.zip
macros/latex/contrib/latex-tds/source.tds.zip
macros/latex/contrib/latex-tds/tds.tds.zip
macros/latex/contrib/latex-tds/tools.tds.zip
Since a few days we have added the respective link to the CTAN web site. Whenever a tds.zip file is present then a download link is provided on the package page and the tex-archive browse page.